Method and apparatus for modulating video signals

ABSTRACT

A luminance component of a video signal is modulated in a first frequency band. A chrominance component of the video signal is modulated in a second frequency band. The modulated luminance component and the modulated chrominance component are then transmitted across a communication link.

TECHNICAL FIELD

[0001] This invention relates to signal processing and, in particular,to systems and methods that modulate multiple video signal componentsfor transmission across a communication link.

BACKGROUND

[0002] Various types of video signals are used to communicate video databetween two devices. For example, composite video is a type of videosignal in which all video data (e.g., the red signals, the blue signals,and the green signals) are mixed together and transmitted across asingle communication link, such as a coaxial cable link. S-Video(Super-Video) signals separate the video data into two separate signals:one for color (chrominance) data, and the other for brightness(luminance) data. When sent to a television or other display device, theS-Video technology generally produces sharper images than compositevideo because the two signals are kept separate from one another suchthat the two signals do not interfere with each other. Another format,referred to as component video, separates the video data into threeseparate signals: the luminance signal, and two chrominance components(labeled P_(R) and P_(B)). Thus, component video signals generallyproduce sharper images than either composite video or S-Video signals.

[0003] Although the S-Video and component video formats usually producesharper images, the video formats cannot be transmitted, or otherwisedistributed, over coaxial cable which is typically found in mostbuilding structures to distribute the video signals. Further, S-Videoand component video cables of arbitrary length are not built into newstructures because the video cable connectors are molded for a betterconnection and the cables cannot be easily routed through walls duringconstruction, or retro-fitted after. Additionally, S-Video and componentvideo cables do not carry audio which must be wired for separately.Thus, in an environment where high quality video signals are to betransmitted (such as in a home network environment), existing videotransmission systems are not adequate.

[0004] Accordingly, there is a need for systems and methods that allowfor the transmission of high quality video signals over long distancesand over existing video cables in a network environment.

SUMMARY

[0005] The systems and methods described herein modulate variouscomponents of a video signal in different frequency bands such that thedifferent video signal components are associated with differentfrequency bands. Since the video signal components are in differentfrequency bands, they are unlikely to interfere with one another, evenwhen transmitted long distances using a common communication link.

[0006] In one embodiment, a luminance component of a video signal ismodulated in a first frequency band. A chrominance component of thevideo signal is modulated in a second frequency band. The modulatedluminance component of the video signal and the modulated chrominancecomponent of the video signal are transmitted across a communicationlink.

[0007] In another embodiment, a luminance component of a video signal ismodulated in a first frequency band. A first chrominance component ofthe video signal is modulated in a second frequency band. A secondchrominance component of the video signal is modulated in a thirdfrequency band. The modulated luminance component of the video signal,the first modulated chrominance component of the video signal, and thesecond modulated chrominance component of the video signal aretransmitted across a communication link.

[0008] In a particular embodiment, a signal is received containing amodulated luminance component and a modulated chrominance component. Themodulated luminance component and the modulated chrominance componentare demodulated. A video signal is generated containing the luminancecomponent and the chrominance component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The same numbers are used throughout the drawings to referencelike features and components.

[0010]FIG. 1 illustrates an example environment in which a modulator anda demodulator process video signals communicated from a client device toa display device.

[0011]FIG. 2 is a block diagram that illustrates components of anexample modulator and an example demodulator.

[0012]FIG. 3 illustrates a flow diagram of a procedure for modulating anS-Video signal.

[0013]FIG. 4 illustrates a flow diagram of a procedure for demodulatinga received signal into an S-Video signal.

[0014]FIG. 5 illustrates an example environment in which a modulator anda demodulator process component video signals communicated from a clientdevice to a display device.

[0015]FIG. 6 is a block diagram that illustrates components of anexample modulator and an example demodulator.

[0016]FIG. 7 illustrates a flow diagram of a procedure for modulating acomponent video signal.

[0017]FIG. 8 illustrates a flow diagram of a procedure for demodulatinga received signal into a component video signal.

DETAILED DESCRIPTION

[0018]FIG. 1 illustrates an exemplary environment 100 in which themethods and systems for modulating video signals may be implemented.Exemplary environment 100 includes a modulator 102 and a demodulator 104implemented to process video signals communicated from a client device106 to a display device, such as television 108.

[0019] In a television-based entertainment and information system, forexample, client device 106 receives television programs and on-demandmovies from a content distribution system via a broadcast network whichmay include a cable television network, RF, microwave, satellite, and/ordata network, such as the Internet, and may also include wired orwireless media using any broadcast format or broadcast protocol. Clientdevice 106 can be implemented as a set-top box, a satellite receiver, aTV recorder with a hard disk, a digital video recorder (DVR) andplayback system, a personal video recorder (PVR) and playback system, agame console, an information appliance, and as any number of similarembodiments. In an alternate system configuration, a client device 106can be coupled to any number of televisions 108 and/or similar devicesthat can be implemented to display or otherwise render content.Similarly, any number of client devices 108 can be coupled to a singletelevision 108.

[0020] In exemplary environment 100, client device 106 communicatesvideo signals to television 108 by generating an S-Video output signalrepresenting a series of video images. The S-Video output signalcontains two separate video components, one component for color (achrominance component 110) and another component for brightness (aluminance component 112). The chrominance component 110 and theluminance component 112 are communicated to modulator 102 whichmodulates the two components into different frequency bands such thatthe two modulated components can be communicated across a singlecommunication link 114 without interfering with one another.Communication link 114 may be a wired or a wireless communication linkusing any type of communication medium.

[0021] Another communication link 116 represents a radio-frequency (RF)communication link between the client device 106 and television 108 tocommunicate such information as remote control selection inputs receivedas viewer commands from a viewer-operated remote control device 118.Remote control selection inputs include volume control commands andchannel change selections that are communicated to client device 106 viatelevision 108, such as when the client device is located in a separateroom from the television.

[0022] The demodulator 104 demodulates the two components of the videosignal to their original values; i.e., a chrominance component 120 and aluminance component 122. The chrominance component 120 and the luminancecomponent 122 are communicated to television 108 to display theassociated video images. Additional details regarding modulator 102 anddemodulator 104 are provided below. The configuration of componentsillustrated in FIG. 1 is particularly useful when client device 106 islocated a distance from television 108 that would require an S-Videocable longer than approximately six feet. In a particular embodiment,client device 106 may be located in a different room or area thantelevision 108. Further, the two components 120 and 122 of the videosignal can be communicated to television 108 over conventional coaxialcable without a degradation of image quality.

[0023] Although FIG. 1 illustrates modulator 102 as a separatecomponent, the modulator may be integrated into client device 106.Similarly, FIG. 1 illustrates demodulator 104 as a separate component.However, demodulator 104 can be integrated into television 108, a videorecording device, or other device.

[0024]FIG. 2 is a block diagram that illustrates components of anexample modulator and an example demodulator. The modulator 102 receivesan S-Video signal from a client device or other source (not shown). TheS-Video signal includes the chrominance component 110 and the luminancecomponent 112. Modulator 102 includes two oscillators 202 and 204, and atone generator 206. The two oscillators 202 and 204 are used to modulatethe two S-Video components 110 and 112 into two different frequencybands. Each frequency band may also be referred to as a “channel”. Thetone generator 206 can be used to determine a phase offset between thevideo signal components that may be incurred during signal processing.

[0025] A common single tone can be modulated as a component of both thechrominance component 110 and the luminance component 112. When thecombined single tone and component signals are de-modulated, the tone isrecovered for both. A variable delay circuit can be implemented toselect varying delays to align the phase of the tone as closely aspossible. Alternatively, the single tone can be generated when power isapplied to the circuit to create a calibration cycle that precludeshaving to combine the tone and the content together.

[0026] Modulator 102 also includes a channel selector 208 that works incombination with the two oscillators 202 and 204 to identify channels orfrequency bands that are available for transmitting the two S-Videocomponents 110 and 112. A transmitter 210 in modulator 102 transmits thetwo modulated S-Video components across a single communication link 212to the demodulator 104.

[0027] The demodulator 104 includes a receiver 214, two oscillators 216and 218, and a transmitter 220. The receiver 214 receives the modulatedS-Video components from the modulator 102 via communication link 212.The two oscillators 216 and 218 are used to demodulate the S-Videocomponents from the received signal.

[0028] Demodulator 104 also includes a tone phase-sense 222 to determineany phase offsets 224 between the chrominance component 110 and theluminance component 112 incurred during signal processing. A delaygenerator 226 in demodulator 104 delays one of the two modulated S-Videocomponents 110 or 112 if needed to properly align the two S-Videocomponents. The delay introduced by delay generator 226 is calculatedbased on the time for each of the signals generated by tone generator206 to propagate between the modulator 102 and the demodulator 104.Transmitter 220 then outputs a chrominance component 228 and a luminancecomponent 230 when the S-Video components are demodulated.

[0029]FIG. 3 illustrates a flow diagram of a procedure 300 formodulating an S-Video signal. Initially, a modulator receives aluminance component and a chrominance component of an S-Video signal(block 302). The luminance component of the S-Video signal is modulatedin a first frequency band (block 304). The chrominance component of theS-Video signal is modulated in a second frequency band (block 306). Thefirst and second frequency bands are different from one another suchthat the two modulated components do not interfere with one another.

[0030] An audio signal (also referred to as an audio portion of thevideo signal) is typically communicated along with a video signal. Inone implementation, the audio signal is mixed or combined with themodulated chrominance component (block 308). The audio signal iscombined with the modulated chrominance component because thechrominance component has a smaller bandwidth and has a frequency thatis considerably different than the frequency of the audio signal. Thus,there is a small likelihood of any significant distortion of the audiosignal by the chrominance component or vice versa.

[0031] Next, the procedure 300 calculates a transmission delay from themodulator to the demodulator (block 310). The procedure then adjusts thetransmission delay of the modulated luminance component or the modulatedchrominance component based on the calculated transmission delay (block312). This adjustment maintains proper alignment of the chrominance andluminance data. Finally, the modulated luminance component and themodulated chrominance component is transmitted across a singletransmission line or a single communication link (block 314).

[0032]FIG. 4 illustrates a flow diagram of a procedure 400 fordemodulating a received signal into an S-Video signal. Initially, ademodulator receives a signal containing a modulated luminance componentand a modulated chrominance component via a single transmission line ora single communication link (block 402). The procedure 400 thenseparates the audio signal from the modulated chrominance component(block 404). The luminance component is then demodulated from thereceived signal (block 406) and the chrominance component is demodulatedfrom the received signal (block 408). An S-Video signal is thengenerated which contains the luminance component and the chrominancecomponent demodulated from the received signal (block 410). The S-Videosignal and the audio signal are then communicated to, for example, atelevision or a recording device (block 412).

[0033] In a particular implementation of the modulator/demodulatorsystem discussed above, the luminance component is a 0-6 Megahertz (MHz)single side band signal which is multiplied by a 30 MHz sine wave,resulting in a 24-36 MHz double side band signal. Since this resultingsignal is radio frequency (RF), it can be efficiently transmitted on asingle transmission line, such as a coaxial cable. Amplitude modulationor frequency modulation may be used to modulate the luminance componentand the chrominance component of the S-Video signal.

[0034]FIG. 5 illustrates an example environment 500 in which a modulator502 and a demodulator 504 are implemented to process component videosignals communicated from client device 106 to television 108. Theenvironment of FIG. 6 is similar to the environment illustrated in FIG.1 and discussed above, but processes component video signals instead ofS-Video signals.

[0035] In example environment 500, client device 106 communicates videosignals to television 108 by generating a component video output signalrepresenting a series of video images. The component video output signalcontains three separate video components, two components for color(P_(R) 506 and P_(B) 508) and another component for brightness (aluminance component 510). The three components are communicated tomodulator 502 which modulates the three components into differentfrequency bands such that the three modulated components can becommunicated across a single communication link 512 without interferingwith one another. Communication link 512 may be a wired or a wirelesscommunication link using any type of communication medium. Anothercommunication link 514 represents a radio-frequency (RF) communicationlink between the client device 106 and television 108 to communicatesuch information as remote control selection inputs received as viewercommands from the viewer-operated remote control device 118.

[0036] The demodulator 504 demodulates the three components to theiroriginal values; i.e., chrominance components P_(R) 516 and P_(B) 518and a luminance component 520. The three components are communicated totelevision 108 to display the associated video images. The configurationof components illustrated in FIG. 5 is particularly useful when clientdevice 106 is located a distance from television 108 that would requirea relatively long component video cable. In a particular embodiment,client device 106 may be located in a different room or area thantelevision 108. Further, the three components 516, 518, and 520 of thevideo signal can be communicated to television 108 over conventionalcoaxial cable without a degradation of image quality.

[0037] Although FIG. 5 illustrates modulator 502 as a separatecomponent, the modulator may be integrated into client device 106.Similarly, FIG. 5 illustrates demodulator 504 as a separate component.However, demodulator 504 can be integrated into television 108, a videorecording device, or other device. Additionally, modulator 502 andmodulator 102 (FIG. 1) may be combined into a single device. Further,demodulator 504 and demodulator 104 (FIG. 1) may be combined into asingle device.

[0038]FIG. 6 is a block diagram that illustrates components of anexample modulator and an example demodulator. The components shown inFIG. 6 are similar to those illustrated in FIG. 2 and discussed above,but process component video signals instead of S-Video signals. Themodulator 502 receives a component video signal from a client device orother source (not shown). The component video signal includes thechrominance components P_(R) 506 and P_(B) 508, and the luminancecomponent 510. Modulator 502 includes three oscillators 602, 604, and606, as well as a tone generator 608. The three oscillators 602, 604,and 606 are used to modulate the three component video components 506,508, and 510, respectively, into three different frequency bands. Eachfrequency band may also be referred to as a “channel”. The tonegenerator can be used to determine a phase offset between the videosignal components that may be incurred during signal processing.

[0039] Modulator 502 also includes a channel selector 610 that works incombination with the three oscillators 602, 604, and 606 to identifychannels or frequency bands that are available for transmitting thethree component video components 506, 508, and 510. A transmitter 612 inmodulator 502 transmits the three modulated component video componentsacross a single communication link 614 to the demodulator 504.

[0040] The demodulator 504 includes a receiver 616, three oscillators618, 620, and 622, and a transmitter 624. The receiver 616 receives themodulated component video components from the modulator 502 viacommunication link 614. The three oscillators 618, 620, and 622 are usedto demodulate the component video components from the received signal.

[0041] Demodulator 504 also includes a tone phase-sense 626 to determineany phase offsets between the video components 506, 508, and 510incurred during signal processing. A delay generator 628 in demodulator504 delays one or more of the three modulated component video components506, 508, and 510 if needed to properly align the three component videocomponents. The delay introduced by delay generator 628 is calculatedbased on the time for each of the signals generated by tone generator608 to propagate between the modulator 502 and the demodulator 504.Transmitter 624 then outputs two chrominance components P_(R) 630 andP_(B) 632, and a luminance component 634.

[0042]FIG. 7 illustrates a flow diagram of a procedure 700 formodulating a component video signal. Initially, a modulator receives aluminance component and two chrominance components (P_(R) and P_(B)) ofa component video signal (block 702). The procedure then modulates theluminance component of the component video signal in a first frequencyband (block 704). The chrominance components (P_(R) and P_(B)) of thecomponent video signal are modulated in a second frequency band and athird frequency band (block 706). An associated audio signal is thenmixed or combined with one of the modulated chrominance components(block 708). The procedure then calculates a transmission delay from themodulator to a demodulator (block 710). The transmission delay of themodulated luminance component or the modulated chrominance components isadjusted, if necessary, based on the calculated transmission delay(block 712). The modulated luminance component and the modulatedchrominance components (P_(R) and P_(B)) are then transmitted across asingle transmission line or communication link (block 714).

[0043]FIG. 8 illustrates a flow diagram of a procedure 800 fordemodulating a received signal into a component video signal. Initially,a demodulator receives a signal containing a modulated luminancecomponent and modulated chrominance components (P_(R) and P_(B)) via asingle transmission line or communication link (block 802). The audiosignal is separated from the modulated chrominance components (block804). The procedure then demodulates the luminance component from thereceived signal (block 806) and demodulates the chrominance components(P_(R) and P_(B)) from the received signal (block 808). At block 810,procedure 800 generates a component video signal that contains theluminance component and the chrominance components (P_(R) and P_(B)).Finally, the component video signal and the audio signal arecommunicated to, for example, a television or a recording device (block812).

[0044] Although the invention has been described in language specific tostructural features and/or methods, it is to be understood that theinvention defined in the appended claims is not necessarily limited tothe specific features or methods described. Rather, the specificfeatures and methods are disclosed as preferred forms of implementingthe claimed invention.

1. A method comprising: modulating a luminance component of a videosignal, wherein the luminance component of the video signal is modulatedin a first frequency band; modulating a chrominance component of thevideo signal, wherein the chrominance component of the video signal ismodulated in a second frequency band; and transmitting the modulatedluminance component of the video signal and the modulated chrominancecomponent of the video signal across a communication link.
 2. A methodas recited in claim 1 wherein the communication link is a singletransmission line.
 3. A method as recited in claim 1 wherein thecommunication link is a wireless communication link.
 4. A method asrecited in claim 1 wherein the first frequency band is different fromthe second frequency band.
 5. A method as recited in claim 1 wherein thevideo signal is an S-Video signal.
 6. A method as recited in claim 1further comprising combining an audio signal with the modulatedchrominance component of the video signal.
 7. A method as recited inclaim 1 further comprising determining a transmission delay to ademodulator.
 8. One or more computer-readable media comprisingcomputer-executable instructions that, when executed, direct a computingsystem to perform the method of claim
 1. 9. A method comprising:modulating a luminance component of a video signal, wherein theluminance component of the video signal is modulated in a firstfrequency band; modulating a first chrominance component of the videosignal, wherein the first chrominance component of the video signal ismodulated in a second frequency band; modulating a second chrominancecomponent of the video signal, wherein the second chrominance componentof the video signal is modulated in a third frequency band; andtransmitting the modulated luminance component of the video signal, thefirst modulated chrominance component of the video signal, and thesecond modulated chrominance component of the video signal across acommunication link.
 10. A method as recited in claim 9 wherein the videosignal is a component video signal.
 11. A method as recited in claim 9wherein the communication link is a single transmission line.
 12. Amethod as recited in claim 9 wherein the communication link is awireless communication link.
 13. A method as recited in claim 9 furthercomprising combining an audio signal with the first modulatedchrominance component of the video signal.
 14. A method as recited inclaim 9 further comprising determining a transmission delay to ademodulator.
 15. One or more computer-readable media comprisingcomputer-executable instructions that, when executed, direct a computingsystem to perform the method of claim
 9. 16. A method comprising:receiving a signal containing a modulated luminance component and amodulated chrominance component; demodulating the modulated luminancecomponent; demodulating the modulated chrominance component; andgenerating an S-Video signal containing the luminance component and thechrominance component.
 17. A method as recited in claim 16 furthercomprising communicating the S-Video signal to a display device.
 18. Amethod as recited in claim 16 further comprising communicating theS-Video signal to a recording device.
 19. A method as recited in claim16 further comprising separating an audio signal from the modulatedchrominance component.
 20. A method as recited in claim 16 furthercomprising: separating an audio signal from the modulated chrominancecomponent; and communicating the S-Video signal and the audio signal toa display device.
 21. One or more computer-readable media comprisingcomputer-executable instructions that, when executed, direct a computingsystem to perform the method of claim
 16. 22. A method comprising:receiving a signal containing a modulated luminance component, a firstmodulated chrominance component, and a second modulated chrominancecomponent; demodulating the modulated luminance component; demodulatingthe first modulated chrominance component; demodulating the secondmodulated chrominance component; and generating a video signalcontaining the luminance component, the first chrominance component, andthe second chrominance component.
 23. A method as recited in claim 22wherein the video signal is a component video signal.
 24. A method asrecited in claim 22 further comprising communicating the video signal toa display device.
 25. A method as recited in claim 22 further comprisingseparating an audio signal from the first modulated chrominancecomponent.
 26. One or more computer-readable media comprisingcomputer-executable instructions that, when executed, direct a computingsystem to perform the method of claim
 22. 27. An apparatus comprising: afirst oscillator configured to modulate a luminance component of a videosignal in a first frequency band; a second oscillator configured tomodulate a chrominance component of a video signal in a second frequencyband; and a transmitter coupled to the first oscillator and the secondoscillator, the transmitter configured to transmit the modulatedluminance component and the modulated chrominance component across acommunication link.
 28. An apparatus as recited in claim 27 furthercomprising a channel selector coupled to the transmitter and configuredto select the first frequency band and the second frequency band.
 29. Anapparatus as recited in claim 27 further comprising a delay generatorcoupled to the transmitter and configured to delay transmission of oneof the components of the video signal.
 30. An apparatus as recited inclaim 27 further comprising a tone generator coupled to the delaygenerator and the transmitter, wherein the tone generator is configuredto generate a tone that is transmitted to a demodulator to determine thedelay in transmitting signals to the demodulator.
 31. An apparatuscomprising: a receiver configured to receive a modulated luminancecomponent and a modulated chrominance component; a first oscillatorconfigured to demodulate the luminance component; a second oscillatorconfigured to demodulate the chrominance component; and a transmittercoupled to the first oscillator and the second oscillator, thetransmitter configured to transmit a video signal containing theluminance component and the chrominance component.
 32. An apparatus asrecited in claim 31 wherein the video signal is an S-Video signal. 33.An apparatus as recited in claim 31 wherein the transmitter transmitsthe video signal containing the luminance component and the chrominancecomponent to a display device.
 34. An apparatus comprising: means forreceiving a modulated luminance component and a modulated chrominancecomponent of a video signal; means for demodulating the modulatedluminance component of the video signal; means for demodulating themodulated chrominance component of the video signal; and means forgenerating an S-Video signal containing the luminance component and thechrominance component.
 35. An apparatus as recited in claim 34 furthercomprising means for communicating the S-Video signal to a displaydevice.
 36. An apparatus as recited in claim 34 further comprising meansfor separating an audio signal from the modulated chrominance component.37. An apparatus as recited in claim 34 further comprising: means forseparating an audio signal from the modulated chrominance component; andmeans for communicating the S-Video signal and the audio signal to adisplay device.
 38. One or more computer-readable media comprisingcomputer executable instructions that, when executed, direct a clientdevice to: modulate a luminance component of a video signal, wherein theluminance component of the video signal is modulated in a firstfrequency band; modulate a chrominance component of the video signal,wherein the chrominance component of the video signal is modulated in asecond frequency band; and transmit the modulated luminance component ofthe video signal and the modulated chrominance component of the videosignal across a communication link.
 39. One or more computer-readablemedia as recited in claim 38 wherein the communication link is a singletransmission line.
 40. One or more computer-readable media as recited inclaim 38 wherein the first frequency band is different from the secondfrequency band.
 41. One or more computer-readable media as recited inclaim 38 wherein the video signal is an S-Video signal.